LL-37 (5mg)

What is LL‑37?

LL‑37 is a human-derived host defense peptide from the cathelicidin family, released as the mature 37-amino-acid fragment of the hCAP18 precursor by neutrophil elastase. It functions as an amphipathic α-helical peptide with broad antimicrobial activity and immunomodulatory capabilities, making it a key subject in research on innate defense, inflammation regulation, and epithelial repair.

Chemical Structure of LL‑37

LL‑37 is a 37–amino-acid peptide with the full sequence Leu–Leu–Gly–Asp–Phe–Phe–Arg–Lys–Ser–Lys–Glu–Lys–Ile–Gly–Lys–Glu–Phe–Lys–Arg–Ile–Val–Gln–Arg–Ile–Lys–Asp–Phe–Leu–Arg–Asn–Leu–Val–Pro–Arg–Thr–Glu–Ser, featuring a helix–bend–helix conformation and significant cationic amphipathicity. It has the molecular formula C₂₀₅H₃₄₀N₆₀O₅₃ and a molecular weight near 4,500 Da. LL‑37 is also referred to as CAMP or hCAP‑18-derived peptide.

What Are the Effects of LL‑37?

In preclinical studies, LL‑37 demonstrates broad-spectrum antimicrobial effects against Gram-negative and Gram-positive bacteria, enveloped viruses, fungi, and biofilm disruption through membrane permeabilization. It also neutralizes microbial toxins (e.g. LPS) and modulates innate immunity by acting on pattern-recognition receptors like FPR2/ALX, promoting chemotaxis of immune cells.

Additionally, LL‑37 supports epithelial cell proliferation and wound closure in lung and skin models, with angiogenic influence through interactions with endothelial pathways. Its dual immunomodulatory activity—enhancing defense while mitigating excess inflammation—is also under active investigation.

Citations

1. PubChem Compound Summary for LL‑37 (CID 3078833): full 37-residue sequence, molecular formula C₂₀₅H₃₄₀N₆₀O₅₃, MW ~4,500 Da. Overview of LL‑37
2. Xhindoli D, et al. “The human antimicrobial peptide LL‑37: a review of functional roles and mechanisms.” Inflamm Res. 2025;74:36. Overview of LL‑37 (via DOI)
3. Steinstrasser L, et al. “Skin electroporation of a plasmid encoding hCAP‑18/LL‑37 promotes wound healing.” Mol Ther. 2014;22(4):734–744. PMID: 24394186. Overview of LL‑37
4. De Y, Chen Q, Schmidt AP, et al. “LL‑37 is a multifunctional modulator of innate immune responses.” J Immunol. 2000;165(6):3268–3275. PMID: 10946509. Overview of LL‑37
5. Brogden KA. “LL‑37: the only human cathelicidin, antimicrobial and immunomodulator.” Nat Rev Microbiol. 2005;3(9):710–720. PMID: 16138053. Overview of LL‑37
6. Noore J, Noore A, Li B. “LL‑37 effectively kills extra- and intracellular Staphylococcus aureus.” Antimicrob Agents Chemother. 2013;57(3):1232–1239. PMID: 23208531. Overview of LL‑37
7. Elssner A, Duncan M, et al. “LL‑37 induces chemotaxis of monocytes and neutrophils via FPRL1.” J Exp Med. 2000;192(7):1069–1072. PMID: 11015447. Overview of LL‑37